George C. Scott is a conservative, religious businessman from Michigan. Everything changes when his daughter is kidnapped and put into pornography films in California. He has to search for her and fight all the scumbags out in California, which happens to include the private detective he hired. It's pretty much the same movie as 8MM (which came 20 years later). Both pretty much serve the same purpose, which is to shock us.
"Hardcore" is quite similar to "Taxi Driver" which has the same screenwriter. Maybe not getting Martin Scorsese to direct this movie was its ultimate flaw. Scorsese can make us like characters no matter how depraved they were. There's no attempt to that here. I don't mean the villains who have kidnapped Scott's daughter (who are one dimensional) but everyone Scott meets in this movie tends to be sleazy and perverted except for him. Even his detective is morally corrupt.